1. Background of the Invention
The present invention relates to a method for producing an optical disk, and more particularly to a method for producing an optical disk having a read-only area and a rewritable area.
2. Description of the Prior Art
An optical disk having a read-only area and a rewritable area is known. Such an optical disk is defined in, for example, the ISO standard. According to the ISO standard, a rewritable area is formed in an inner area of the optical disk, and a read-only area is formed in an outer area thereof. The rewritable area has a magneto-optic recording medium on which tracks are formed. The read-only area has pits formed on a recording medium.
Japanese Laid-Open Patent Application No. 2-101925 discloses an optical disk which has a file address management area formed in an innermost area of the optical disk. The file address management area includes information indicating directory tracks. A read-only area is formed further out than the file address management area, and a rewritable area is formed further out than the read-only area. The above optical disk is called a partially-read-only optical disk. A similar optical disk is also disclosed in Japanese Laid-Open Patent Application No. 4-1979.
Information is recorded on and read from the optical disk while the optical disk is being rotated at a constant angular velocity. In this case, the linear speed measured at an outer portion of the optical disk is greater than that measured at an inner portion thereof. Hence, a laser beam for recording information on the rewritable area needs a large amount of power because the rewritable area is rotated at a high velocity. Normally, the power of the laser beam used for recording is greater than that for reading. A tracking servo control of the rewritable area is carried out using grooves arranged in the circular direction of the optical disk. The linear velocity of the rewritable area formed in the outer area of the optical disk is great; hence, the response of the tracking servo control is low. This may cause tracking errors.
An optical disk in which the read-only area is further out than the rewritable area does not have the above-mentioned problems. In this case, the file address management area is formed further in than the rewritable area. According to general disk management operating systems, files are sequentially recorded on the optical disk from the inner area to the outer area. In other words, files are recorded on the optical disk from an idle recording area located further in than other idle recording areas. When information is written into the read-only area during the production process, it is necessary for the rewritable area to be filled with files. In the rewritable area, the addresses of files written into the rewritable area are registered from the innermost inner portion of the file address management area, and the addresses of files written into the rewritable area are registered so as to be subsequent to the addresses of files in the read-only area. If the rewritable area has unused portions, the address information concerning the read-only area cannot be registered in the file address management area.